Children exposed to air pollution caused by vehicles are at an increased risk of developing schizophrenia: Study
Schizophrenia is a highly heritable psychiatric disorder, and researchers now believe that exposure to nitrogen dioxide—an air pollutant—during childhood is associated with an increased risk of subsequently developing the disorder.
Schizophrenia is a severe mental disorder that affects more than 21 million people worldwide.
The research team led by Aarhus University, Denmark—which studied people for ten years—found that a 10 microgram per cubic meter (μg/m3) increase in childhood daily nitrogen dioxide exposure was associated with increased schizophrenia risk.
“We found a correlation between childhood nitrogen dioxide exposure and polygenic (genetic) risk score for schizophrenia, and we confirmed that both were associated with an elevated risk of schizophrenia. A 10-μg/m3 increase in childhood daily nitrogen dioxide exposure was independently associated with increased schizophrenia risk,” says the study published in JAMA Network Open.
Air pollution is now the world’s largest single environmental health risk, with 91% of the global population living in places where pollutant levels exceed the World Health Organization (WHO) limits. Exposure to air pollution is associated with adverse health effects, including increased risk of death.
“In 2016, 91% of the world population was living in places where the WHO air quality guidelines levels were not met. Ambient (outdoor air pollution) in both cities and rural areas was estimated to cause 4.2 million premature deaths worldwide in 2016,” says the WHO.
Based on expert evaluation of current scientific evidence, the WHO currently has air quality guidelines for particulate matter, ozone, nitrogen dioxide, and sulfur dioxide.
Nitrogen dioxide belongs to a group of gaseous air pollutants produced by road traffic and as a by-product of combustion, says the research team.
“Epidemiological studies have shown that symptoms of bronchitis in asthmatic children increase in association with long-term exposure to nitrogen dioxide. Reduced lung function growth is also linked to nitrogen dioxide at concentrations currently measured (or observed) in cities of Europe and North America,” says the WHO.
The study was conducted using data from the Danish Civil Registration System, which was established in 1968. All those born in Denmark between May 1, 1981, and December 31, 2002, were followed up from their 10th birthday until the first occurrence of schizophrenia, death, or December 31, 2012, whichever came first.
During the study period, of a total of 23,355 individuals, 3,531 were diagnosed with schizophrenia. According to the analysis, individuals exposed to daily nitrogen dioxide levels of 25 micrograms per cubic meter or higher during childhood had a higher risk compared with individuals exposed to daily levels of less than 10 micrograms per cubic meter.
This study found that childhood nitrogen dioxide exposure was associated with an elevated risk of schizophrenia that was only slightly explained by a polygenic (genetic) risk score for schizophrenia,” the findings state.